1. Field of the Invention
The present invention relates to a highly productive and efficient process for producing a perfluoroalkyne compound useful as a dry-etching gas or a CVD gas used in semiconductor device manufacturing or as a raw material for a fluorine-containing polymer.
2. Description of Related Art
Recently, there has been increased demand for a technology for a dry-etching gas and a CVD gas used in manufacturing semiconductor devices along with an increase in the degree of integration and the performance of semiconductor devices, as seen in very-large-scale integrated (VLSI) circuits, ultra-large-scale integrated (ULSI) circuits, and the like. In order to satisfy such a demand, various compounds having a better quality have been studied.
For example, Patent Document 1 discloses hexafluoro-2-butyne having a triple bond in a molecule as a gas for forming a fluorinated amorphous carbon insulating film having a low dielectric constant. Patent Document 2 discloses that octafluoro-2-pentyne having a triple bond in a molecule is useful as a dry-etching gas for forming a high aspect ratio contact hole.
As a process for preparing a perfluoroalkyne compound having a triple bond in a molecule, Patent Document 3, for example, discloses a process of obtaining a target product, octafluoro-2-pentyne, by treating 2,3-dihydrodecafluoropentane with an alkali.
However, 2,3-dihydrodecafluoropentane used as a raw material has been reported to be harmful to the environment since its atmospheric lifetime is 17 years and its (100-year) global warming potential (GWP) value is as high as 1300.
Non-patent Document 1 discloses the following process of preparing hexafluoro-2-butyne. First, trifluoroiodomethane is added to 3,3,3-trifluoropropene tb obtain 2-iodohexafluorobutane. Then, 2-iodohexafluorobutane is treated with an alkali to obtain hexafluoro-2-butene. Chlorine or bromine is added to hexafluoro-2-butene to obtain 2,3-dihalohexafluorobutane. Finally, 2,3-dihalohexafluorobutane is treated twice with an alkali to obtain hexafluoro-2-butyne.
However, the process disclosed in the document has many problems when manufacturing the product industrially, because trifluoroiodomethane and 3,3,3-trifluoropropene are industrially procured only with difficulty and the process has many production steps. Therefore, the process is not practical.    Patent Document 1: JP-A-9-237783    Patent Document 2: US-A-2005101140    Patent Document 3: US-A-2005092240    Non-patent Document 1: Journal of Chemical Society, p. 2504 (1952)